Reply to the Letter to the Editor: Percutaneous Doxycycline Treatment of Aneurysmal Bone Cysts With Low Recurrence Rate: A Preliminary Report

To the Editor,

We are grateful to see interest in this technique and its utilization in the treatment of bone cysts. Before responding to this letter to the editor [4], it needs to be said that the one of the authors of the paper under discussion [3], Dr. Shiels, passed away in 2015 shortly after publication. We have published additional case series [2, 5] on smaller subsets of patients treated with this technique and have recently presented a 14-year look back [1] of a much larger group of primarily extremity aneurysmal bone cysts. These reports mention how bone-void fillers mixed with doxycycline can be used for the exact same reasons that Dr. Stone describes [4], though we did not focus on it specifically in our analyses.

Using bone-void fillers mixed with antibiotics is a common practice in orthopaedic surgery for treating or preventing infections, and it makes sense to apply them to the treatment of aneurysmal bone cysts for many of the same reasons. We have not conducted an in-depth analysis of the nuances of utilizations and outcomes of bone-void fillers in aneurysmal bone cysts because we have treated several hundred aneurysmal bone cysts, including patients of many ages with lesions in nearly every bone in the body, making a rigorous analysis impractical.

Over the past 20 years, we have used at least seven different bone-void fillers mixed with doxycycline that vary in composition, making them functionally similar. For the purposes of percutaneous sclerotherapy, the bone-void filler needs to be made into a slurry that will fit through relatively small needles (14G in our hands), needs to be miscible with all other agents used, needs to be visible by imaging when in use, and needs to be safe. Further discussion of the risks and merits of different bone-void fillers is too big a topic for this reply, but we think it is important to point out that these agents come and go, can be variably available, and, very importantly, can range over 10-fold in per-unit cost.

Lastly, these agents are relatively easy to use for large unilocular lesions in extremities but become much more problematic in multicystic, partly solid, or expansile lesions, and are especially difficult in locations like the skull, spine, or within joints where extrusion is dangerous. Ultimately, the operator needs to choose when to use a bone-void filler and which one to use based upon his or her comfort with the chosen agent, the lesion location, the technique, and the availability and cost of the bone-void filler.